Blast Furnace Conditions Research Articles

Characterization of the burden behaviour of iron ore pellets mixed with nut coke under simulated blast furnace conditions

ABSTRACTIn the blast furnace, nut coke is utilized in a mixture with the ferrous burden to improve the gas permeability. Although applied in a broad range (10–40 mm, 2–23 wt-%), limited information is available on changed burden behaviour in its presence. In the present study, the detailed characterization was performed on the iron ore pellets quenched during sintering, softening and before complete melting. The quantified information of the phase distribution across the pellets is compared for the samples mixed with and without nut coke. The principal role played by the nut coke is on bringing higher reduction and lower sintering among the pellets. For the pellet mixed with nut coke, at the core, ∼25 vol.-% of the material is observed in a network arrangement. The core structure consists of a wüstite matrix (10–20 vol.-%) reinforced with the iron nuclei (5–15 vol.-%). On the contrary, in the absence of nut coke, the pellet core is observed being hollow.

Experiment Research on Pulverized Coal Combustion in the Tuyere of Oxygen Blast Furnace

Abstract The actual combustion rate of pulverized coal in the blast furnace tuyere is hard to be measured. In this research, the combustion rate of pulverized coal injected into oxygen blast furnace was obtained by a new equipment. This equipment can simulate the actual blast furnace well, and the relationship between pulverized coal injection (PCI) ratio and AO/C was established by mathematical deduction. The experimental results show that the best combustibility of the four pulverized coals is C, and when the coal injection ratio is 350 kg/tHM, the combustion rate can be reached 79%, while the combustion rate of B in the same case is only 45.6%. With the increase of AO/C , the relative amount of oxygen to coal increases, the combustion conditions become better, and combustion rate of the pulverized coal increases. In addition, under the condition of high temperature and rapid combustion, with the increase of coal’s volatile, the combustion rate increases and the corresponding PCI ratio is also increased. By using the new equipment, the unburned coal under the oxygen blast furnace conditions can be collected for further study.

Occurrence and Behavior of Sulfur‐Bearing Minerals in Metallurgical Coke

The behavior of sulfur‐bearing minerals is characterized from coking coals to the feed coke and the blast furnace (BF) coke using field emission scanning electron microscope and thermodynamic calculations. In coals, they are represented by sulfides (pyrite, sphalerite, galena, chalcopyrite, and arsenopyrite) and sulfates (anhydrite and barite). During coking process, the minerals undergo phase transformations, but sulfur will be retained in the coke in mineral form for most of the minerals until the end of the coking process. Depending on the initial mineral in the coal, sulfur‐bearing minerals will be transformed at the end of coking process into the following phases: pyrrhotite, wurtzite, Cu–Fe–S melt, CaS, and BaS. The amount of sulfur that will be kept in the coke in mineral form increases in the following order: galena → pyrite → sphalerite → arsenopyrite → chalcopyrite → anhydrite → barite. Intensive gas flow under BF conditions facilitates liberation of sulfur from mineral phases in the Fe–S and Zn–S system. CaS and BaS are the most stable sulfur‐bearing phases formed after sulfur‐bearings minerals. The coals with elevated amounts of anhydrite and barite, or with high concentrations of Ca and Ba combined with S should be avoided for coking purposes. Complete elimination of mineral‐related sulfur from coke under BF conditions occurs above 2000 °C.

Effect of Natural Gas Injection Point on Combustion and Gasification Efficiency of Pulverized Coal under Blast Furnace Condition

Effect of Natural Gas Injection Point on Combustion and Gasification Efficiency of Pulverized Coal under Blast Furnace Condition

Application of the improved the ELM algorithm for prediction of blast furnace gas utilization rate

Blast furnace gas utilization rate is one of the indicators for measuring the smooth operation of the blast furnace. The prediction model of the blast furnace gas utilization rate based on the extreme learning machine algorithm (ELM) is firstly established. The burden surface characteristics and the indexes of the blast furnace condition are the input parameters, and the blast furnace gas utilization rate is the output parameter. In most cases, the regular item factor is introduced for ELM to ensure satisfactory output. In this paper, the same prediction model based on PCA-ELM algorithm which is based on the principal component analysis method (PCA) and ELM is established secondly. Real production data of the blast furnace is used to verify the prediction model. By comparing with the results of two models, the model based on the PCA-ELM algorithm has better accuracy than that based on ELM.

Coke Quality and Blast-Furnace Performance

On the basis of six-year operational data for a 5000-m3 blast furnace, the dependence of the coke consumption on its strength M25 and M10 and the content of the >80 mm fraction is calculated by different methods. The quality of the coke has a clear influence on coke consumption and blast-furnace economics. As an illustration, for some of the equations derived, means are established for predicting the economic benefit associated with improving coke quality and reducing its consumption, in specific blast-furnace conditions.

Computational Fluid Dynamics Study of Biomass Combustion in a Simulated Ironmaking Blast Furnace: Effect of the Particle Shape

Biomass is a carbon-neutral fuel and has a potential to be used in pulverized coal injection (PCI) technology in ironmaking blast furnaces (BFs). Compared with pulverized coal particles, biomass particles vary considerably in particle shape, and thus the change of aspect ratio of biomass particles may affect the motion and conversion of biomass particles. In this study, a computational fluid dynamics (CFD) model is developed to simulate the flow and thermo-chemical behaviors related to biomass injection into BFs. The model features non-spherical particle shapes and an improved devolatilization model. The model is then applied to a pilot-scale test of charcoal injection using a pilot-scale PCI test rig under simulated BF conditions for model validation. The burnout comparisons between simulation and measurement indicate that compared to spherical particles, the non-spherical particles show smaller burnouts due to the shorter travelling time in the chamber; moreover, the burnouts predicted by the model cons...

Effect of diboron trioxide on the crushing strength and smelting mechanism of high-chromium vanadium–titanium magnetite pellets

The effect of diboron trioxide (B2O3) on the crushing strength and smelting mechanism of high-chromium vanadium–titanium magnetite pellets was investigated in this work. The main characterization methods were X-ray fluorescence, inductively coupled plasma–atomic emission spectroscopy, mercury injection porosimetry, X-ray diffraction, metallographic microscopy, and scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results showed that the crushing strength increased greatly with increasing B2O3 content and that the increase in crushing strength was strongly correlated with a decrease in porosity, the formation of liquid phases, and the growth and recrystallization consolidation of hematite crystalline grains. The smelting properties were measured under simulated blast furnace conditions; the results showed that the smelting properties within a certain B2O3 content range were improved and optimized except in the softening stage. The valuable element B was easily transformed to the slag, and this phenomenon became increasingly evident with increasing B2O3 content. The formation of Ti(C,N) was mostly avoided, and the slag and melted iron were separated well during smelting with the addition of B2O3. The size increase of the melted iron was consistent with the gradual optimization of the dripping characteristics with increasing B2O3 content.

Study on the Equilibrium of Slag and Hot Metal at Tapping with Respect to Sulfur

The blast furnace slag and hot metal are collected from the industrial trials. The collected slag and hot metal samples are re‐melted in a graphite crucible and stirred to investigate the sulfur partition at different stirring times. The experimental oxygen potential is well controlled to simulate the blast furnace conditions. The results show evidently that sulfur is transferred from hot metal to slag, which lead to an increase in the sulfur partition from its initial value (t = 0 min) of 26–33 at 1743 K, and from 23 to 37 at 1773 K after 30 min of slag‐metal reaction. The results strongly indicate non‐equilibrium between slag and hot metal at tapping. The sulfide capacities of the slag with typical composition of the slag at tapping are determined. On the basis of the sulfide capacity data, the theoretical sulfur partition is evaluated. The theoretically calculated partition further supports the finding obtained in the stirring experiments. This finding would suggest the possibility of improvement to increase the usage of blast furnace slag in desulfurization.

Effect of charcoal addition on the properties of a coke subjected to simulated blast furnace conditions

A pilot oven produced coke with the addition of 7.5wt% charcoal (bio-coke) and the similarly produced base blend coke were subjected to gasification and annealing under the simulated blast furnace conditions. The effect of charcoal addition on the coke properties after gasification and annealing was characterised using Raman spectroscopy, ultra-micro indentation and tensile testing. The addition of charcoal significantly increased the coke reactivity with CO2 as a result of its increased surface area by charcoal. The addition of charcoal made no further contribution to the devolatilisation or mineral reactions of coke during annealing. The charcoal particles were well preserved after annealing at 2273K, but preferentially consumed in the gasification. Annealing temperature had less effect on the graphitisation of the charcoal component compared to the coexisting inert maceral derived component (IMDC) and reactive maceral derived component (RMDC). The charcoal addition had no effect on the microstructure and microstrength of coexisting microtextural types during annealing and gasification. The charcoal presented a higher resistance to fracture than IMDC and RMDC under annealing conditions. The addition of charcoal did not deteriorate the coke resistance to strength degradation under the thermal load of blast furnace. However, charcoal addition caused more severe degradation by gasification as demonstrated by more reduction in the tensile strength of the bio-coke. This was attributed to the preferential solution loss reaction of the charcoal particles leaving voids which coalesced the pores in coke, thereby increasing the defects that cause stress concentration under loading.

Investigation of Reduction Mechanism and Kinetics of Vanadium Titanomagnetite Carbon Composite Hot Briquette at 1173-1373 K

The isothermal reduction of vanadium titanomagnetite carbon composite hot briquette, simulated Blast Furnace condition at the temperature range of 1173–1373 K, is investigated in an electric resistance furnace. The samples reduced at different temperature are characterized by X-ray diffraction (XRD). The phase transitions during reduction process can be described as follows: Fe3O4 → FeO → Fe; Fe2.75Ti0.25O4 → Fe2.5Ti0.5O4 → Fe2TiO4 → FeTiO3 → TiO2; FeTiO3 → TiO2; Fe2VO4 → V2O3; FeCr2O4 → Cr2O3. Then, model fitting methods are used to evaluate the apparent activation energy during this process. The reduction process can be divided into three stages, and the apparent activation energies of the three stages are 40.26, 66.46, and 90.96 kJ mol−1, respectively. The rate controlling step of the initial stage is gas diffusion and interfacial chemical reaction. However, as the reduction proceeding, the rate controlling steps of the intermediate and final stage are gradually transformed to interfacial chemical reaction.

Modelling the injection of upgraded brown coals in an ironmaking blast furnace

Victorian brown coal is a low-cost and abundant resource, featuring in high moisture and low ash yield, and has a potential of replacing high grade metallurgical coals in pulverized coal injection (PCI) in ironmaking blast furnace (BF). In this paper, a three-dimensional mathematical model is used to simulate the flow and thermochemical behaviours related to the PCI operation of upgraded Victorian brown coals under full-scale BF conditions. The model geometry covers lance, blowpipe, tuyere, raceway and coke bed at the lower part of a BF. The typical phenomena of in-furnace aerodynamics and physicochemical behaviours relevant to the injection of Victorian brown coals are simulated, in terms of flow, temperature, gas composition and coal combustion characteristics. It is indicated that the model is able to predict the combustion phenomena of Victorian brown coals under BF conditions. The performance between one typical PCI coal and two upgraded brown coals by briquetting and pyrolysis, respectively, are compared. The results indicate the upgraded Victorian brown coal by pyrolysis under given conditions has demonstrated the similar combustion profile with the PCI coal, confirming the feasibility of replacing PCI coal with an upgraded brown coal. Compared with the other two coals, briquetted brown coal of relatively higher volatile matter (VM) led to the release of more fuel gas, thus consuming more oxygen and achieving higher temperature along the tuyere axial and along the raceway boundary. Faster combustion of briquetted brown coal also led to higher overall burnout around the raceway region. The model provides a cost-effective tool to optimize and control the injection of Victoria brown coals under industry-scale BF conditions.

Ignitability and combustibility of Yallourn pyrolysis char under simulated blast furnace conditions

In this paper we have examined the potential of Yallourn brown coal char (collected from an industry-scale pyrolyser) to be used as a pulverized coal injection (PCI) fuel, its size-dependent properties, ignitability and combustibility under the simulated conditions of the blowpipe-tuyere section in a blast furnace. The combustion of individual sizes for Yallourn char was tested in a lab-scale drop-tube furnace (DTF) using pre-heated hot gas with a temperature up to 1000°C, and a particle residence time as short as 0.6s. Computational fluid dynamics (CFD) modelling was further conducted to optimize the char combustion conditions via sensitivity analysis. Irrespective of the pyrolysis condition, Yallourn char is superior over bituminous coal for being used as a top grade PCI fuel, due to its higher calorific value (7500–8110kcal/kg), lower ash content (<10wt%), high ash melting temperatures (>1550°C), and abundance of iron (>40wt% in ash). The performance of Yallourn char is also superior over bituminous coal under the simulated blast furnace conditions, for a rapid ignition and burnout even for a coarse char size of 300μm under the stoichiometric O2/C molar ratio and using low blast temperatures of 800–1000°C. All these are beneficial for reducing the energy consumption related to particle pulverization and the amount of oxygen for the combustion. With regard to the Yallourn char ignition and combustion in the hot gas, a minimum 6wt% volatile content is essential for a stable and rapid ignition of the volatiles at a gas temperature of 1000°C or below, since homogeneous ignition is predominant at low temperatures. However, once the blast temperature rises to 1200°C, the dependence on volatile content turns insignificant due to the dominance of the heterogeneous ignition, high C-O2 reactivity for the solid char, as well as the minimized pore diffusion control due to the large porosity (52.0–63.1%) of the Yallourn char tested here.

Study on the interaction behaviour between lump and sinter under the condition of oxygen blast furnace

This research report describes the influence of the reducing atmosphere of oxygen blast furnace (OBF) and traditional blast furnace (TBF) on the softening and melting behaviour of lump and lump-sinter mixed burdens assessed by using the softening and melting test. The results reveal that in the OBF atmosphere, the softening and melting properties of lump ore is improved compared with that of the TBF, since the development of reduction degree increased the quantity of the iron phase in the burden particle, and decreased the quantity of slag phase with low melting temperature. In addition, the analysis on the microstructure of burden particles revealed that the interaction effect also occurred at the interface between lump and sinter particles in OBF case. Meanwhile, the scanning electron microscope images shows that the interface is still distinguishable when the samples of OBF case reached 60% contraction ratio (1379°C), whereas in the case of TBF, the interface almost disappeared above 40% contraction, and became completely undistinguishable at 60% contraction ratio (1290°C). This illustrates that, under the OBF condition, the starting temperature of interaction is raised, and the effect intensity is weakened.

Gasification Reaction Characteristics of Ferro-Coke at Elevated Temperatures

Abstract In this paper, the effects of temperature and atmosphere on the gasification reaction of ferro-coke were investigated in consideration of the actual blast furnace conditions. Besides, the microstructure of the cokes was observed by scanning electron microscope (SEM). It is found that the weight loss of ferro-coke during the gasification reaction is significantly enhanced in the case of increasing either the reaction temperature or the CO2 concentration. Furthermore, compared with the normal type of metallurgical coke, ferro-coke exhibits a higher weight loss when they are gasified at the same temperature or under the same atmosphere. As to the microstructure, inside the reacted ferro-coke are a large amount of pores. Contrary to the normal coke, the proportions of the large-size pores and the through holes are greatly increased after gasification, giving rise to thinner pore walls and hence a degradation in coke strength after reaction (CSR).

A Novel Technique for Making Cold Briquettes for Charging in Blast Furnace

Different metallurgical wastes are generated during pyro processing of iron ore, which is used for making sponge iron or hot metal and for producing steel. Apart from these wastes, coke fines are generated during the coke making, and iron ore fines are generated during mining of iron ore. Although iron ore fines are used for making pellet after beneficiation still, it generates a huge quantity of iron ore waste during beneficiation with comparatively lower iron content. In the present study, briquettes are made by a stiff extrusion process from metallurgical waste like iron ore fines and coke fines with the addition of Portland cement as a binder and clay as a rheology modifier. Physical properties of the briquettes are evaluated, and reducibility of the briquettes is studied in comparison to lumpy iron ore. Phase analysis and microstructural analysis of the briquettes and lumpy iron ore are carried out after firing at different temperatures in the simulated blast furnace condition. Physical and mineralogical properties are correlated with the reducibility of the briquettes and lumpy iron ore. Briquettes made by a stiff extrusion process show a better mechanical strength fired at a different temperature to take the load of burden and better reducibility than lumpy iron ore. The briquettes after self-curing are charged to a 23 mt3 blast furnace which shows encouraging results.

Ignitability and Combustibility of Yallourn Pyrolysis Char Blended with Pulverized Coal Injection Coal under Simulated Blast Furnace Conditions

Pulverized coal injection (PCI) is a widely used blast furnace technology aimed at reducing costs and increasing productivity. The prospect of blending PCI coal with a lower cost char, derived from Yallourn brown coal, is evaluated in this study by means of thermogravimetric analysis (TGA), flat-flame burner reactor, and drop-tube furnace experiments at four different blending ratios as well as computational fluid dynamics (CFD) modeling. Yallourn char has desirable properties compared to PCI coal, including a lower ash content and a higher heating value, although the reactivity is lower and the ignition temperature is higher. Because the combustion behavior of a blend is not always easily predicable based on the performance of the individual parent fuels, two Yallourn char samples (YC-1 and YC-2) are analyzed after blending with PCI coal at four ratios. According to the particle ignition time, a maximum of 40 wt % is allowable for YC-1 char which is comparably reactive with the commercial PCI coal. Howev...

Coke Degradation under Simulated Blast Furnace Conditions

Three metallurgical cokes made from coking coals over a significant range in rank were subjected to treatment with blast furnace-like gas composition-temperature profile to 1 673 K, annealing under N2 to 2 273 K and gasification with subsequent annealing at 1 873 and 2 273 K. The degradation of cokes after reaction and annealing was characterised using I-drum tumbling, tensile testing, ultra-micro indentation and X-ray diffraction. Both gasification and annealing decreased the mechanical strength of coke. Compared with annealing at 1 673 K, gasification at same temperature caused larger degradation for all three cokes, and the effect was more significant on more reactive coke. In the annealing process, degradation of the cokes occurred through the entire coke lump and resulted in both tensile strength and I-drum tumbling strength decreasing simultaneously. In the process of gasification under the blast furnace-like conditions, degradation took place through the whole piece of coke with high reactivity; however, the degradation of coke with low reactivity was more severe at the periphery than in the core and therefore gasification had a minimal effect on the core of the coke and its tensile strength, but had a much stronger effect on I600. Microstrength of coke decreased significantly with increasing annealing temperature. The change of microstrength of coke upon gasification, which occurred at relatively low temperatures, was marginal. The cokes after gasification with subsequent annealing had similar microstrength and graphitisation degree compared to those subjected only to annealing at the same temperature.

Changes in Pore Structure of Metallurgical Cokes under Blast Furnace Conditions

Metallurgical cokes were subjected to gasification by CO–CO2–N2 gas with blast-furnace-like composition–temperature profile to 1673 K (1400 °C) and annealing under N2 at temperature up to 2273 K (2000 °C). Pore structure of cokes was examined using image analysis. Porosity and pore size were both enlarged under gasification and annealing conditions. The pore structure change during gasification was mainly a result of the Boudouard reaction; the pore structure development upon annealing was attributed to the reactions of mineral matters with carbon and further devolatilization. Annealing and gasification caused a decrease in average pore roundness, an increase in the fraction of low roundness pores and the increase of coalescence points in the pore area. The degradation of coke strength following reaction and annealing was characterized using tensile testing. Both gasification and annealing decreased the mechanical strength of coke. Degradation of more reactive cokes (cokes C and D) by gasification at 1673...

Modelling of injecting a ternary coal blend into a model ironmaking blast furnace

The operation of ironmaking blast furnaces (BFs) involves several minerals such as iron ore, coals and flux. The practice of injecting a coal blend is widely employed in ironmaking BFs, typically binary blend or ternary blend. It is desirable to understand the overall performance of a coal blend and their individual behaviours of component coals. In this paper, a three-dimensional CFD model is described to simulate the flow and combustion of a ternary coal blend under simplified BF conditions. Three component coals in the ternary blend are tracked separately and undergo chemical reactions individually. The overall performance of ternary coal blend and individual behaviours of three component coals are analysed over the entire domain and quantified along the chamber axis, respectively, with special reference to flow, temperature, gas species and coal combustion efficiency. The simulation results show that generally, an inclined high-speed gas jet and coal plume are formed along the axis followed by an expansion and recirculation near the wall, resulting in the higher temperature and lower O2 at the lower part of the chamber. Individually, the coal of higher VM content devolatilises faster, shows larger particle size downstream, and reaches a higher burnout and a slightly higher particle temperature in the end. The non-addition is observed in predicting the burnout of the ternary coal blend due to the interactions among three component coals. The model provides an effective tool for ternary blend’s design and operation optimisation in ironmaking BFs.